Abstract: New prostheses for ligaments and tendons in humans or animals intended to replace deficient original organs and induce the growth of new-formed tissue, which tissue, in turn, replaces such a prosthesis and reconstitutes an analogue of the original organ, may comprise at least one strand of synthetic polyaramide fibres NOMEX (i.e. polymetaphenylene isophthalamide the fibres not having any having any protective element so that they are placed in direct contact with surrounding live tissues, as a result of which the growth of fibrous new-formed tissue is induced to replace the synthetic fibres which are at least partly eliminated.